Device for controlling the propagation of energy in a wave guide



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M. D. FISKE 2,505,534 DEVICE FOR CONTROLLING THE PROPAGATION OF' ENERGY IN A WAVE GUIDE Filed April 27, 1945 2 Sheets-Sheet 1.

FE1 Page im Hol j E i); f

His AttoT-n e131.

Amm 2 Filed April 27. 1943 M. D. 'HSKE DEVICE FOR CONTROLL NG THE PROPAGATION 0F ENERGY IN A WAVE GUIDE 2 Sheets-Sheet 2 Inventor: Milan D. Fiske,

His Attorneg.

Patented pr. 25,

DEVEDE` EFG?, GNTRGLLING HE PR01*ASML-f TIN 9F ENERGY EN A WAVE GUIDE' Milan E. Fiske, Schenectady, N. Y., assigner toi General Electric Company, a corporation of New York if Claims.`

My invention relates to ultra high frequency systems, and more particularly to arrangements for controlling the propagation of electromagnetic Waves through dielectric wave guides of the hollow-pipe type;

It is an object of my invention to provide new and improved arrangements for controlling the propagation of electromagnetic Waves through dielectric wave guides ofthe hollow-pipe type.

It is another object `of my invention to provide new and improved arrangements including elec tric discharge devices for controlling the wave propagating characteristics of tuned apertures positioned in dielectric wave guides of the hollow-pipe type.

It is a further object of my invention to provide new and improved tuned aperture constructions comprising electric discharge devices for controlling or tuning such apertures positioned Within dielectric Wave guides.

It is a still further object ci my invention to provide a new and improved system for tuning a resonant aperture positioned within a dielectric Wave guide in accordance vviththe frequency of the energization of the dielectric wave guide.

Briefly stated, in accordance with one aspect of the present invention, I provide new and improved constructions for resonant apertures which are associated or positioned Within dielectric 4Wave guides of the hollow-pipe type and by means of which the energization of the dielectric Wave guide is controllable. provide a unitary electric discharge device, either of the high vacuum type or of the type employing an ionizable medium such as a gas or a medium, which is insertable in the body of a transverse member positioned in the guide and which is in communication with a tuned or resonant aperture. The electric discharge device comprises a plurality of enclosed electrodes, such as an anode and a cathode, establishing a region of charged electrical particles associated with a part or all of the aperture, thereby controlling or tuning its characteristics.

One form of resonant aperture which is contemplated is that in which the capacitive part ci the aperture is principally furnished by means of a central slot terminated at each end in an elongated central opening, such as a circular opening. tioned within the guide or may be displaced towards the top, the bottom, or sides of the memberv defining the dielectricwave guide.

In accordance with a further aspect of my invention, I'provide a system including as an ele- More specifically, I-

The aperture may be centrally posi i.

ment thereof a'tuneable or controllable aperture in a dielectric wave guide and in which the Wave guide may be operated over a range of frequencies. For example, the dielectric Wave guide may be energized either by alocal high frequency generator or oscillator, or by radiation receiving means, and the wave propagating characteristics of the wave guide, and particularly the Wave transmitting characteristics of the aperture, are controlled or tuned by means of an electric discharge device. Means are `provided for control# ling the electric discharge between theelectrodes for establishing a region of charged electrical particles, the density of which controls the electrical characteristics of the apertune. In this manner, the waveguide and associated' structure are selectively responsive to electromagnetic waves of a predetermined frequency or range of` frequencies, consequently effecting transmission of such waves and producing substantial relecu tion of electromagneticwaves outside this range.

The present invention relates to improvements in ultra high frequency control systems of the nature disclosed and broadly claimed in my joint United States Letters Patent No.- 2,413,963, granted Januar-y 7, 1947, and which isassigned to the assignee of the present application.

For a better` understanding of my invention; reference may be had to tliefollowing description taken in connection lWith the accompanying? drawings, and its scope lwill be pointed out in the appended claims.` Fig; l" diag-rammaticallyillustrates an embodimentof' my invention wherein an electric discharge device isinsertable Within and' lies in thebody of a transverse member which deiines a tuned aperture, and Fig. 2 is a cross sectional end view of the arrangement shown in Fig. 1. Fig. 3' is another modification wherein the principal axisfo'f the electric dis@ charge device is substantially` parallel and coincident with the principal axis ofthe tuned a'pere ture and in which the aperture is displaced to-r wards one side of the dielectric wave guide; Fig; 4 is a cross'sectional` longitudinal? view showing a part of the dielectric Wave guide and the transverse member supporting the' electric discharge device envelope. Fig. 5 is a still further modication in which the aperture is position-ed in th' edge of the transverse memberl adjacent inner! surface of the conductive'member which defines the Wave guide. Fig. 6 'represents one type of system to which my invention may beapplied and which comprises a controllable ultra high ire--` quency generator or oscillator, the-'aperture by means ofthe electric discharge device being con-'- 3 trolled in response to the output frequency of the oscillator.

Referring now to Figs. 1 and 2 jointly of the accompanying drawings, my invention is there illustrated as applied to a dielectric wave guide which may be of rectangular cross section defined by a conductive member I in which electromagnetic waves are to be propagated, reflected or controlled. Although my invention is applicable to electromagnetic waves generally both of the transverse electric and transverse magnetic types, for the purpose of facilitating the description of my invention the comments are directed to a system for the transmission of a transverse electric Hoi type wave wherein the electric component of the eld is transverse to the direction of wave propagation and is substantially perpendicular to the top and bottom of the member l as illustrated.

Within the member l, I provide a transverse partition or member 2 of conductive character preferably comprising a solid piece of metal such as a block of copper or brass provided with a tuned aperture which optionally may be positioned centrally with respect to the member l. l,

The tuned aperture may include a central elongated slot 3 which constitutes principally the capacitance of the aperture and is terminated at the ends thereof in elongated openings such as circular openings 4 and 5 which constitute principally the inductance of the aperture. It is to be understood that the particular conguration of the aperture, so far as the instant invention is concerned, is not critical, it of course being understood that apertures of various congurations are contemplated, the criterion being that the dimensions of such apertures are chosen or established to control or tune the aperture to be resonant to electromagnetic Waves of a predetermined frequency.

The transverse member 2 is provided with a channel or opening 6 preferably lying within the body of member 2 and which is in communication with the above described tuned aperture. One position which this opening may assume is that illustrated in Fig. 2 wherein the principal axis of the openingis substant ally perpendicular to the principal dimension of the aperture and in which the aperture intersects the centrally positioned slot 3. Opening t may be made exter nally accessible by providing member i with openings 'l and 3 at the top and bottom thereof to permit the insertion of an electric discharge device to be described presently.

As a means for controlling the electrical characteristics, particularly the wave propagating or transmitting characteristics, of the dielectric Wave guide and particularly the aperture, I provide a unitary electric discharge device 9 preferably comprising an elongated dielectric or vitreous envelope lll of such cross sectional configuration, at least in part, to permit ready insertion Within openings S, 1, and 8. These openings as well as the cross section of envelope it may be circular, the dimensions of the openings 6, l, and 8 relative to the outside dimension of envelope lil being such that a close t is obtained Without establishing a restriction on the insertion and extraction of the discharge device.

The electric discharge device 9 may be either of the high vacuum type or of the type employing an ionizable medium, such as a gas or a vapor. For the purpose of illustrating my invention, I have chosen to show an electric discharge device in which the ionizable medium is a gas or a vapor and which comprises a plurality of electrodes such as an anode H and a cathode l2 the latter of which may be of the thermionic type comprising a fllamentary heating element.

Electric discharge devices employed in systems of this nature may be of controlled character, that is, provided with control members such as electrostatic grids the potentials of which control the electric discharge present within the vicinity of the tuned aperture. Where the electric discharge device is of the gaseous type, the density of the particles constituting the discharge between the anode and cathode may be controlled by Varying the voltage impressed across the anode and cathode derived from a suitable variable voltage source such as a battery i3 which may be connected to the anode and cathode through a circuit controlling means, such as a switch lll.

When it is desired to employ a high vacuum type discharge device, the device may be of the grid controlled type in which instance the magnitude of the space charge may be varied or controlled in response to a predetermined controlling inuence by means of the grid potential.

If it be considered that an electromagnetic wave is established within the wave guide l and if no discharge is present within the envelope lil, due to the tuned or resonant condition of the aperture electromagnetic waves will be propagated through the aperture. The mechanism by v.'rtue of which this transmission or propagation of waves takes place may be considered from an elementary point of view as comprising the establishment of an accentuated voltage across the top and the bottom of the aperture due to the transverse electric component of the waves caused by the impingement of the Waves on the forward side of the transverse member 2 facing the travelling wave. This voltage difference is, of course, present on the tralling side of the transverse member and serves to excite the remaining part of the guide to establish a. travelling wave in that part of the guide. Due to the resonant nature of the slot, the impedance oiered to the travelling wave is relatively small, the transverse wall and the slot offering a minimum discontinuity or change in impedance.

The estabLshment of an electric discharge between the anode I i' and cathode l2 serves to ccntrc-l or detune the aperture. Investigation of the reflection properties of this type arrangement reveals that reflection increases and transmission decreases with increase either in the discharge current or the amplitude of the guided waves incident upon the aperture. Measurements of the ampltude reilection factor r and amplitude transmission factor t, under condi-v 'tions with a substantial power output available L from a local oscillator and with a unidirectional discharge current of one ampere through an electric discharge device having a 1/8 inch diameter envelope, indicated a value of 1'=G.97 and t=0.l5; that is, 94 per cent of the energy was reected, 0.3 per cent was transmitted, and approximately 5.7 per cent was lost in the discharge device and the metal surrounding the aperture.

In considering the tuning eiect of the electric discharge on the aperture, it may be viewed generally in the following manner, The presence of the charged electrical particles serves to control the eifective dielectric constant or the medium within the slot, particularly the space between the upper and lower edges of the central 75 portion which primarily controls the capacitance of the aperture. As the density of the electrical particles constituting the discharge is rlcrdased, the effective dielectric constant of the medium decreases and consequently the natural frequency of `the structure changes, thereby providing an arrangement for rendering the structure selectively responsive to predetermined different frequencies, each frequency being a function of the density of the particles for a xed geometry of the aperture.

Another modification of my invention is il1us.- trated in Figs. 3 and 4 Which will be considered jointly. Fig. 3 is a transverse cross sectional view and Fig. 4 is a longitudinal cross sectional View. In the arrangement shown in Figs. 3 and 4, the transverse member 2 is provided with a tuned aperture which may have a dumb-bell longitudinal shape, such as that described above in connection with Figs. l and 2, and the aperture may bedisplaced towards one side as illustrated. Thel elements of the arrangement shown in Figs. 3 and 4 have been assigned reference numerals corresponding to like elements in Figs. l and 2. In this modification, the transverse member 2 and the Wave guide defining member i are arranged to permit lateral insertion of the electric` dise charge device l, so that the principal axis of the discharge device is substantially parallel withand preferably coincident with the axis of the tuned aperture and a transverse cylindrical opening l5 which provides an externally accessible channel Within which part of the discharge device 9 rests. It is to be noted that in this modification of my invention, by virtue of the positioning of anode l I and cathode l2, the region of charged electrical` particles incident to the discharge between these electrodes extends substantially the entire length of the aperture.

A further modification is illustrated in Fig. 5 which is a transverse cross sectional view and in Which the transverse member 2 is provided with a` tuned aperture Which lies in the edge, such as the upper edge, of member and adjacent an inner surface of member l. The aperture may comprise a central opening le terminated at each end. in enlarged openings Il and i8, and the boundaries of the aperture as a whole comprise the related surfaces of transverse member 2 and the cooperating inner surface of the top of member I. The provision or the tuned aperture neer the edge or at the edge of the transverse member makes it possible to utilize a relatively short spacing between the electrodes, such as an anode I and a cathode 2u of an electric discharge device comprising an enclosing envelope such as a vitreous or dielectric envelope 2i which is insertable in theI position illustrated through a transverse vertical opening 22 and associated .openings 23 and Eil in the top and bottom of member i.

I have illustrated in Fig. 6 one manner in which my invention may be applied tc an ultra high frequency system where it is desired to control the Wave propagating characteristics of a dielectric wave guide 2li to render the system selectively responsive to electromagnetic .vaves of predetermined freduency. rhe dielectric wave guide 25 comprises a controlling means, such as that illustrated in l, and corresponding elements have been assigned like reference numerals.

In some types of transmitting and receiving systems utilizing ultra high frequency electromagnetic waves, it is desired to employ a range of operating frequencies or different frequencies. For example, in systems of this character which are employed for detecting the presenceof o blil and the reception of a reflected Wave, it is of portance to provide arrangements for changing the transmitting frequency to prevent jamming, The system described hereinafter is ap plicable to arrangements of that nature inasmuch as the structure lends itself readily to the control of electrical characteristics of the wave guide, and particularly the aperture, to maintain the aperture tuned to any one of a predetermined number of operating frequencies.

The dielectric Wave guide may be employed as a high frequency transmitting channel interconnecting an antenna, a receiver, and a. high frequency generator. The control means comprising the resonant aperture is positioned in the dielectric Wave guide to protect the receiver during operation by the transmitter or generator. The relative positions of the receiver, connection to the antenna (not shown) and the resonant aperture are illustrated in Fig. 6.

The dielectric wave guide 25 may be provided with an electrode means which may serve as an exciting means for the wave gulde, or as a means for deriving energy from the guide. This electrode means may comprise a transverse member or Wire 26 Which is electrically connected to the top of the guide and constitutes an extension of a concentric transmission line 21 including an inner conductor 28 and an outer tubular c-onductor 29.

In those applications where a local generator or oscillator is employed, the concentric transmission line 2l may be connected thereto. A local oscillator 30 may be employed, and for the purpose of illustrating one form of such oscillator or generator, I have chosen to represent diagrammatcally to reduced scale an ultra high frequency magnetron of the type disclosed and claimed in United States Letters Patent No. 2,412,824, granted December i7, 1946, and which is assigned to the assignee of the present application. The magnetron comprises a metallic enclosing tubular envelope 3| having therein an anode structure 32 provided with a `plurality of annular-ly positioned l space resonant cavities or regions 33 which are in communication with an enlarged central opening 34 through a plurality of radially extending slots (not shown). A thermionic cathode 35 is posi' tioned within the central opening and comis provided by a pair of permanently magnetized pole pieces 35 and 3l which are supported by members attached to the tubular envelope 3-I. Energy is extracted from the space resonant regions 33 by an output electrode shown generallyV a at 38 and is connected to inner conductor 2S of transmission line 2l.

The output frequency of the generator 3Q may One vvay in which this may y be controllable. be accomplished is by control of the eifective natural frequency of the space resonant regions 33. Such frequency control may be attained by means of a positionable member 33 externally operable v;

by means of a rod ci).

the aperturev One way in which this control may b accomplished is by variation in the magnitude.

of the voltage impressed across anode ii and cathode l2 in response to such controlling influence. As an example of an arrangement which may be employed for this purpose, I may employ a resistance 4| across which a variable unidirectional potential is produced by means of an amplier such as a high vacuum triode i2 energized from a suitable source of current, such as a battery 43. The potential of grid tf: controls the magnitude of the anode-cathode current and consequently controls the voltage applied across resistance 4|.

Where it is desired to control the density oi the particles in the discharge current transmitted between anode Ii and cathode l2 in response to the output frequency of generator I may employ a tuned circuit 1&5 of the concentric conductor type comprising an cuter tubular conductor 46 and an inner conductor il?, and which is provided With input electrode means iS connected to transmission line 2i through a concentric transmission line 49, and output electrode means 5i? which constitutes an extension of an inner conductor 5I of a concentric transmission line comprising the inner conductor 5l and outer tubular conductor 52.

The resonant circuit :i5 is preierabiy chosen to have an electrical length corresponding to a haii wave length, or multiples thereof, of a particun larly operating frequency. of the circuit i5 and hence its resonant frequency may be controlled by suitable means, such as a plunger 53 provided with actuating rods 51%.

A unidirectional voltage which is a function of the magnitude of the exciting frequency may be provided by the utilization of resistance 55 which is energized from output electrode means 5i? by means of a crystal rectifier 56. Ii desired, a by-passing capacitance 5i may be connected to transmission line 52 as illustrated. The unidirectional voltage appearing across resistance 55, or a portion thereof, may be employed to control the conductivity of the high vacuum triode t2. For example, a predetermined component of this volt age may be employed to operate against a fixed biasing Voltage, such as that provided by battery 58, to control automatically the density of the electrical particles within the vicinity of the aperture.

Considering the operation of the system shown in Fig. 6, let it be assumed that the system is initially adjusted to render the aperture in transverse disk 2 resonant to a predetermined irequency. This resonance may be accomplished by the joint characteristics of the incident electrical discharge and the geometry of the aperture. If for any reason the operating frequency of the system changes, the density of the charged elec-` trical particles is controlled in the proper direction to maintain this desired resonance.

For a particular adjustment of plunger 5t to render circuit l5 resonant to a given frequency, a deviation of operating frequency produces a change in the energization of circuit l5 and particularly a change in the magnitude of the magnetic field intensity at the output electrode means 5U, causing a corresponding change in the voltage which appears across resistance 55. This voltage is then effective to control the conductivity of triode 42 and consequently produces the desired direction of change in the intensity of the electric discharge between anode i! and catliode I2.

The above described automatic tuning feature The electrical length is'fof considerable importance for controlling the energization of the receiver. Inasmuch as the received signal in the wave guide 25 derived from the antenna is usually of insufcient amplitude to alter appreciably the density of the charged electrical particles Within the envelope I0, the control of the density of these particles is eiecti-ve in establishing selective frequency response for the energization of the receiver.

During the transmitting operation, that is, during the intervals during which the generator 30 operates or transmits power to the antenna through dielectric wave guide 25, the receiver connected beyond the resonant aperture structure is not energized inasmuch as the relatively largeV intensity of the electromagnetic waves within the guide due to the energization is sumcient to cause a breakdown or discharge across the resonant aperture structure, that is, across the electrode parts of transverse member 2 deiining the resonant aperture.

intensity of the generated electromagnetic waves may be suniciently great to cause some ionization of the medium within the envelope I0. I-Iowever,

in the event a high vacuum discharge device is employed, the ionization is established principally across the slot in transverse member 2. In this manner, the receiver is protected during operation of the transmitter. However, as stated above, upon reception of the relatively weak received signals when the generator 3G is not operating, the receiver is energized through the resonant aperture structure. Furthermore, the resonant aperture structure is automatically tuned for these weak signals received by the system by the means including the frequency responsive elements and the electric discharge device 9, thereby rendering the receiver always receptive to waves corresponding to the operating frequency of the generator.

One of the important advantages of the above described type of constructions for the resonantV discharge device, thereby substantially eliminating any Ipossibility of electrode sputtering which would otherwise be eiective or present if the mef tallic parts of the transverse member 2 were employed as electrode parts of the controlled electric discharge path.

While I have illustrated my invention as including various devices diagrammatically illustrated, it will be obvious to those skilled in the art that changes and modications may be made without departing from my invention, and I therefore aim in the appended claims to cover all such changes and modications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a dielectric wave guide of the hollow-pipe type defined by a conductive k member, a transverse conductive member within said guide and having an aperture tuned to a particular frequency of electro-magnetic waves within said guide, and means for controlling the wave propagating characteristics of said aperture comprising an electric discharge device lying substantially wholly within the body of said trans- Where an electric discharge de-j vice using an ionizable medium is employed, the

verse member and extending across said aperture, said discharge device including an elongated dielectric envelope and a plurality of enclosed electrodes.

2. In combination, a dielectric Wave guide of the hollow-pipe type defined by a conductive member, a transverse conductive member positioned Within said guide and having a resonant aperture the principal dimension of which is transverse to the electric component or" the electromagnetic Waves within said guide, said transverse member having a second opening therein substantially perpendicular to said aperture and extending therethrough, and an electric discharge device positioned within said opening and substantially entirely enclosed Within said member and comprising an elongated dielectric envelope having therein a plurality of electrodes for establishing a region of charged electrical particles for controlling the Wave propagating characteristics of said aperture.

3. In combination, a dielectric Wave guide of the hollow-pipe type defined by a conductive member, a transverse conductive member within said guide provided with a resonant aperture comprising .a central slot and a pair of enlarged openings at each end thereof, said transverse member being provided with a central cylindrical opening the axis of which is substantially perpendicular to said slot, and an electric discharge device within said cylindrical opening and extending across a portion of said slot and comprising an elongated tubular envelope substantially entirely enclosed within said member and including a plurality of electrodes for establishing a region of charged electrical particles Within said slot.

4. In combination, a dielectric wave guide f the hollow-pipe type defined by a conductive member, a transverse conductive member Within said guide and having an aperture tuned to a particular frequency of electromagnetic waves within said guide, said aperture comprising a central slot terminated at each end in an enlarged opening, and means for controlling the wave propagating characteristics of said aperture comprising a unitary electric discharge device lying substantially entirely within the body of said transverse member for establishing a region of charged electrical particles extending throughout substantially the entire length of said aperture.

5. In combination, a dielectric wave guide of the hollow-pipe type defined by a conductive member, a transverse conductive member Within said guide and having an aperture tuned to a particular frequency of electromagnetic Waves Within said guide, means for controlling the Wave propagating characteristics of said aperture comprising an electric discharge device supported within the electric field adjacent said aperture for establishing a region of charged electrical particles within the vicinity of said aperture, means comprising an ultra high frequency generator for exciting said guide, and means for controlling said electric discharge device in accordance with the output frequency of said generator for controlling the energizaton of said guide beyond said aperture.

6. In combination, a dielectric wave guide of the hollow-pipe type defined by a conductive member, a transverse conductive member Within said guide and having an aperture tuned to a particular frequency of electromagnetic Waves within said guide, means for controlling the Wave propagating characteristics of said aperture comprising an electric discharge device supported within the electric eld adjacent said aperture for establishing a region of charged electrical particles within the vicnitiy of said aperture, means comprising an ultra high frequency generator for exciting said guide, and frequency responsive means for controlling said electric discharge device in accordance with the output frequency of said generator.

7. In combination, a dielectric Wave guide of the hollow-pipe type dened by a conductive member, a transverse conductive member within said guide and having an aperture tuned to a particular frequency of electromagnetic Waves within said guide, means for controlling the Wave propagating characteristics of said aperture comprising an electric discharge device supported within the electric field adjacent said aperture for establishing a region of charged electrical particles within the vicinity of said aperture, means comprising an ultra high frequency generator for exciting said guide, means for controlling the frequency of said generator, and means for controlling said electric discharge device in accordance with the output frequency of said generator for controlling the energization of said guide beyond said aperture.

MILAN D. FISKE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,035,958 Girardeau Aug. 20, 1912 2,284,405 McArthur May 26, 1942 2,308,523 Llewellyn Jan.4 19, 1943 2,403,302 Richmond July 2, 1946 2,403,303 Richmond July 2, 1946 2,407,068 Fiske et al Sept. 3, 1946 2,408,425 Jenks Oct. l, 1946 2,413,171 Clifford Dec. 24, 1946 2,413,963 Fiske et al Jan. '7, 1947 2,432,093 Fox Dec. 9, 1947 FOREIGN PATENTS Number Country Date 114,102 Australia Nov. 6, 1941 

